Gas detector apparatus



July 14, 1953 v c. TIFFANY 2,645,564

GAS DETECTOR APPARATUS Filed April 26. 1950 $1 mmvrm CA RT; E Tl FFA N Y. B Y

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ATTORNEYS.

Patented July 14, 1953 UNITED STATES PATENT OFFICE GAS DETECTOR APPARATUS Carter Tifiany, Englewood, N. J.

Application April 26, 1950, Serial No. 158,313

7 Claims. 1

This invention relates to gas detectors, and more particularly to improvements in such detectors employing a catalytic agent for generating heat in response to the presence of a combustible vapor such as hydrocarbon vapor and oxygen.

Apparatus of this character suggested in the past for detecting the presence of hydrocarbon vapors has been unusually expensive and inconvenient to use and also has failed to provide a detector which will indicate immediately the presence of such vapor in a satisfactory manner;

Furthermore, such gas detectors suggested in the past have not lent themselves to mass production techniques and have been encumbered with complicated measuring apparatus of a delicate nature which may easily become maladjusted. Furthermore, apparatus of this character previously suggested has been disadvantageously affected by changes of ambient temperature, for example, changes in air temperature due to weather changes.

Moreover, minor voltage fluctuations occurring in apparatus of this type employing electrical circuits have required extraordinarily delicate adjustment by an operator in order to maintain a desired accuracy of the device.

One of the objects of the present invention is to overcome the above difficulties or to reduce same to insignificance.

The invention in one aspect thereof includes a pair of wire elements having preferably equal resistances which are held under tension by suitable means and in series in an electrical circuit, by which such wires are heatable. The wires are selected to have equal expansion for a common increase in temperature. A catalytic agent is associated with one of the two wires, such agent being capable of inducing an exothermic reaction in the presence of a combustible vapor such as hydrocarbon vapor with oxygen. In the presence of, for example, air containing a hydrocarbon vapor, the wire element having a catalytic agent associated therewithis heated to a higher temperature than the other wire and consequently elongates a different and greater amount than the other wire, that is, there is an expansion differential between the wire elements. Means are operatively associated with said wires under tension for producing a signal in response to the occurrence of such a differential in expansion. Under normal conditions, when no hydrocarbon vapor is present, the wire elements maintain their same relative length since both are affected equally by changes in ambient temperature and by fluctuations of voltage.

The invention in another aspect thereof is constituted by the combination of a pair of thermoresponsive wire elements, each having an extremity thereof secured to an arm, the opposite extremity of each of said wire elements being held in relatively close relation to but spaced from a base extremity of said arm. Means are employed for exerting upon the base extremity of the arm an axial thrust whereby the wire elements are maintained under tension and are held substantially in a Vformation with the supporting arm therebetween. The arm is angularly shiftable about the base extremity thereof but is restrained from such motion, except in the event of an expansion differential in the wires, by such wires which hold same in place. An electric circuit is provided which includes the thermo-responsive wire elements connected preferably in series. The wire elements are equally expansible for a given increase in temperature and are heatable by a common source of electrical energy in said circuit. A catalytic agent is mounted in contact with one of said wire elements for heating same in response to the occurrence of a hydrocarbon vapor in the presence of an oxygen-containing gas, such as air, whereby such heat augments the heat generated in the wire by the electrical power source. Thus an expansion differential between the two wire elements can occur when such elements are in the presence of the hydrocarbon vapor and oxygen, the arm being angularly shiftable in response to such an expansion differential. Suitable means, such as a switch, can be operatively associated with the supporting arm and actuatable by angular movement thereof whereby a signal device can be controlled in response to the presence of such hydrocarbon vapor. Instead of employing a catalytic agent in contact with one of the wires, it is possible to employ one wire of catalytic material, such as platinum, the other wire being non-catalytic with respect to such vapor.

Various, further and more specific objects, features and advantages of the invention will clearly appear from the detailed description given below taken in connection with the accompanying drawings which form a part of the specification and illustrate, by way of example, preferred arrangements of apparatus for carrying out the invention. The latter consists of such novel combinations and features as may be shown and described in connection with the device herein disclosed.

In the drawings:

Fig. 1 constitutes a plan view of a device embodying one form of the invention;

Referring to the drawings in further detail,

heat expansible wires are shown at H} and II. They are associated with means for holding them under equal tension and are incorporated in an electric circuit, to appear more fully hereinafter;

a portion of the base member i2, form two adjacent acute substantially right triangles having adjacent acute angle apices at the outer extremity of the signal arm where the wires ill and il are seciued thereto. The invention, however, is not limited to the precise lengths of the wires IE7 and l l and the signal arm 43 as shown inFig. 1. For example, the signal arm 13 may be somewhat shorter and one of the wires 10 or H may be longer than the other. However, where such change in dimension occurs, it will be understood that there are still two adjacent right triof electrical energy. Each wire is of equal electrical resistance and under normal conditionsofno-gas, that is, of no hydrocarbon vapor, they are of equal expansion and contraction characteristics with respect to a common temperature change.

The wire 10 may be of platinum which constitutes a catalytic agent with respect to a hydrocarbon vapor in the presence ofv an oxygen-containing gas, such as air. The wire [I may be of a non-catalytic metal with respect to these gases, such as Nichrome. The respective diameters of the wires are selected to give each equal electrical resistance.

Suitable means are provided for magnifying or amplifying an expansion differential between the wires I5 and II which, in the form shown, is constituted by a so-called v-tension mounting. This term refers to means for maintaining the wire elements it and H under tension and in a substantial l-formation wherebya magnification of the expansion differential is effected. The -tension mounting is constituted by a base member [2 and, in the form shown, a signal arm 53. One extremity of each of the wires l and H is secured to the base member l2 as at M and Ma. The opposite extremities of the wires Iii and H are secured to the outer extremity of the si nal arm l3, for example, through the intermediary of a collar 15,.and such extremities are electrically interconnected. Collar I .is rigidly secured to arm [3 as by pin a and is preferably of electrically conducting material.

The opposite extremity of the signal arm, that is, the base extremity thereof, is associated with the base member [2 preferably at a point approximately midway between the wire anchorage points It and Ma. The means for associating the base extremity of the signal arm 13 with the base member constitutes, in the form shown, a spherical hearing or member, as at 16, about which the arm I3 may shift angularly when such motion is permitted by an expansion differential between the wires l0 and I I, said spheri cal member 16 being urged downwardly, as viewed in Fig. 1, by means of a helical spring, as at H, which is contained within a cylindrical sleeve l8, as is the sphere 56. The pressure exerted upon the signal arm it may be adjusted by controlling an adjustment screw H which is in threaded engagement within the sleeve l8 and engages one extremity of the helical spring ll. An essential characteristic of the aforementioned l-tension mounting consists in the separation of the pivoted or base extremity of the signal arm from that extremity to which are secured the wires ID and l l It will be understood that in the particular embodiment shown in Fig. 1 the wires [8 and H, together with the signal arm.l3.and

angles formed by virtue of a line extending from the inner or base extremity of the wire It or II perpendicular to the axis of the signal arm I3,

portions of such latter axis being common to the two adjacent acute triangles. Where it is hereinafter mentioned that two adjacent acute substantially right triangles are formed by such wires H3, II and signal arm l3 it is understood that the right angle nature thereof exists by virtue of such lines extending from the base extremity of each of the wires l0 and H perpendicular to the axis of the signal arm 13.

, If desired, it is not necessary for the wire H] to be of a catalytic substance, such as platinum, and for the other wire II to be of a non-catalytic substance. That is, it is possible for both of the wires to be, for example, of Nichrome steel and to surround one of the wires with a catalytic substance, such as finely divided platinum held by a neutral substance such as asbestos, a ceramic material, or gum arabic, the catalyst being held in close contact with the wire.

The base member l2 may be of metal or it may be of a suitable insulating material. If the base member is of metal, the extremities of the wires ill and H secured thereto at [4 and Ma are insulated from such base member, for example, by passing the extremities of the wires through suitable perforations in the base member, the sides of which the wires do not contact, and welding glassballs, as at [4b and [40, to such extremities, respectively.

If desired, the signal arm [3 may be of glass or of a metallic substance such as steel. Also, instead of maintaining the wire elements Hi and H under tension by means of an arm thrust outwardly away from and mounted in the base member l2, it is possible to maintain such elements under tension by means of suitable resilient means which pull the wires into tension located below the member [5 (Fig. l).

The base member I 2 above described comprises a bracket which is secured to a main frame or foundation member 29, the latter preferably being of an electrically nonconducting material, such as a suitable plastic.

The extremities of the wire elements 10 and H, as at 14 and Ma, are preferably connected to suitable terminal members, as at 2| and 22, respectively, which facilitate the connection of the device into a suitable electric circuit to appear below.

In the form of the invention shown in the drawings, a switching device is employed which is operatively associated with the signal arm l3 and is responsive to angular movements thereof which in turn occur in response to said expansion differential between wires 10 and H.

The signal arm I 3 accordingly is operatively associated with a switch member 23 which may govern suitable signal means to be described hereinafter. The switch 23 may be of a so-called singlelpole, double. throw variety and preferably is of the type known as a microswitch. Ihe latter switch is provided with an actuating arm 24 having a contactfinger or member 25 atthe outer extremity thereof which maybe located near the collar or-contact member [5 above described, the latter being rigidly secured to the signal arm 13. The actuating arm 24 is associated with a plunger 26 for actuating the'switch 23. The latter switch is mounted in an adjustable manner upon the foundation member 20, that is, it is mounted upon an adjustable arm 23a which is pivotally mounted at 21 to such foundation member 20,

the opposite extremity of the arm 23a beingi slotted as at 231) and associated with an adjustment nut 28 in a well known manner whereby the switch may be adjustably positioned toward or away from the signal arm l3, thereby adjusting the relative positions of the contact finger 25 and the collar I5.

The embodiment of the invention shown in Figs. 1 and 2 may be connected in a simple electrical circuit having a common source of electrical energy for heating the wire elements l and H, the element It! being of platinum or of, for example, Nichrome, and having surrounding same a catalytic agent such as finely divided platinum whereby wire element 10 is of unequal expansion and contraction characteristics relative to the wire I I when in the presence of a hydrocarbon' vapor and air. Such hydrocarbon vapor and air will act upon the platinum whether it is the platinum in the wire or the finely divided platinum and will augment the heat generated by such electrical circuit whereby the outer extremity of the signal arm, that is, the lower extremity thereof, as viewed in Fig. 1, will be shifted to the right and the signal arm l3 will thus angularly shift in a counterclockwise direction, whereby the switch 23 will be actuated for the purpose of controlling a suitable signal means for indicating the presence of the hydrocarbon vapor.

It has been found advantageous to have the distance between the points [4 and [4a approximately one-half inch and the length of the sig-- nal arm I3, from the midpoint of the base line between such points l4 and Ma. to the collar [5, approximately three inches. That is, the distance from the distance from the mid-point of the base line between points l4 and Ma to, for example, point i4, is preferably about one-twelfth of the distance from such mid-point to the pin l5a. Such an arrangement will give a magnification of the expansion differential of the order of about one to twelve.

There is shown in Fig. 3 one form of an electrical circuit in which the wire elements l0 and H may be connected, said circuit comprising a lead 29 which interconnects the terminals 2| and 22 above described, there being interposed in the lead 29 a source of electric energy, such as the battery 30, a manually operable switch 3!, and the above-described microswitch 23, which normally is closed. A signal means, such as an incandescent lamp as at 32, may be connected in parallel with the wires [0 and i i by means of the lead 33 in the manner shown. Thus the following electrical circuit is created when the switches 23 and 3| are closed: From the battery 30 through the switch 3|, the switch 23, the wires ll, 10, and thence to the battery 30. When the switch 23 is open as a result of an expansion differential between the wires l0 and II, it is obvious that the signal lamp 32 will be extinguished.

If desired, the switch actuating arm 24 may be electrically connected to the terminal 22 as by the lead 34 whereby, through the intermediary of the electrically conducting collar IF), the wire element Il may be shunted when the collar l5 contacts the finger 25 of the switch arm 24.

The length and diameter of the wires 10 and II are so selected that their electrical resistance to a given electrical load will increase their respective temperatures as high as possible commensurate with the mechanical load placed upon them by the helical spring l7.

In operation, it will be seen that in the presence of air or other oxygen-bearing gas containing a hydrocarbon vapor Or other combustible gas, the wire ID will be heated to a higher temperature than the wire ll. Because of the catalytic action of the hydrocarbon vapor upon the wire I0, if it is platinum, or upon the catalytic agent, such as the finely divided platinum surrounding the wire, if the latter is of a noncat alytic nature, an expansion of the wire [0 will take place over and above that of the wire II. By virtue of the so-called V-tension mounting of the wires in and l l, a small increase in the length of the wire l0 causes the end of the signal arm [3 carrying the collar or contact l5 to move a relatively long distance and to bring the collar i5 into contact with the finger 25. Such engaging of collar 15 and finger 25 shunts the wire ll, allowing it to cool, and since the wire In now offers the bulk of the resistance to the flow of current, its temperature will be rapidly increased and a substantial difierential of heat between the wires will occur and will cause the contact end of the signal arm l3, that is, the outer extremity [5, to move a sufficient distance to actuate the switch 23 whereby it is opened and the incandescent light 32 is extinguished.

It will be seen that the gap between the collar l5 and the finger 25 controls the sensitivity of the device and since this gap is adjustable, the sensitivity of the apparatus can be easily pre-adjusted when the apparatus is manufactured or later when in use.

It will be understood that other means may be employed for controlling a signal device in response to a shifting of the signal arm I3 or in response to a differential of expansion between the wire elements [0 and l I. For example, a mechanical leverage system may be employed for amplifying the movement of the outer extremity of the signal arm [3 in order to give a quantitative indication of the explosive vapor concentration. Also it is possible to employ optical means in combination with the apparatus, for example, a mirror may be mounted upon the signal arm [3 which may be shifted angularly therewith which, with the assistance of a light beam reflected thereupon, may give an indication of the explosive vapor concentration, such light beam being directed upon a suitably calibrated scale. Also it is possible to employ suitable light sensitive device such, as a photoelectric cell, which may be actuated in response to a moving light beam controlled by a mirror mounted as above suggested, such a light sensitive device being operatively associated with suitable signal means for giving an indication of the explosive vapor.

While the invention has been described with respect to certain preferred examples which have given satisfactory results, it will be understood by those skilled in the art, after understanding the invention, that various changes may be made and various modifications effected without departing from the spirit and scope of the invention, and it is intended, therefore, in the appended claims to cover all such changes and modifications.

What is claimed as new and is desired to be secured by Letters Patent is:

1. In apparatus for the detection of hydrocarbon vapors, a pair of wire elements; an arm having secured to an outer extremity thereof an extremity of each of said wire elements, a base member, the opposite extremity of each of said wire elements being secured to said base in close relation to but spaced from a base extremity of said arm and on opposite sides of the longitudinal axis thereof; means for pivotally mounting such base extremity of such arm; means for exerting upon the base extremity of said arm an axial thrust to maintain said wire elements under tension, the latter being held substantially in V- formation, said wire elements and the axis of said arm forming, together with lines perpendicular to such axis extending to such opposite extremities of said wires, two adjacent acute substantially right triangles having adjacent acute angle apices and having common side portions in such axis of said arm; an electric circuit including said wire elements connected in series, said elements being equally expansible for a given increase in temperature and being heatable by a common source of electrical energy in said circuit; one of said wire elements constructed to include a catalyst for heating same in response to the occurrence of a combustible vapor in the presence of an oxygen-containing gas, an expansion differential between said two elements occurring when such elements are in the presence of such vapor and gas, said arm being angularly shiftable about said base extremity in response to such an expansion differential; and signal means actuatable in response to angular movement of said arm.

2. Apparatus comprising in combination, a base member; a pair of thermo-responsive expansible wire elements mounted with one extremity of each thereof secured to said base member at separate locations whereby a straight base line exists between such locations; a signal arm having the other extremities of said wire elements secured adjacent one extremity of such arm; means for mounting the opposite extremity of said arm for r pivotal and axial movement in the region of said base member substantially at the mid-point of such base line, means for resiliently urging said arm axially for maintaining said wire elements under tension, said wire elements, arm and base line defining two adjacent acute substantially right triangles having adjacent apices and having a common side comprising said signal arm; one of said wire elements being constructed to include a catalytic element comprising finely divided platinum for heating same in response to the occurrence of a hydrocarbon vapor in the presence of oxygen whereby an expansion differential may occur between such elements in the presence of such gases, said arm being angularly shiftable in response to such expansion differential; and signal means actuatable in response to such angular movement of such signal arm.

3. In apparatus for the detection of hydrocarbon vapors, a base member; a signal arm; a pair of wire elements having equal expansion and contraction characteristics responsive to a common temperature change therein, one of said wire elements constructed to include a catalyst for heating same in response to the occurrence in the surrounding atmosphere of hydrocarbon vapor and oxygen, said wire elements each having a base and an outer extremity, the base extremities of each of said wire elements being spaced apart and secured to said base member, the outer extremities of said wire elements being secured to said signal arm near one extremity thereof; means located substantially on the axis of said arm and in the region of said base memher for mounting the opposite extremity of said arm for pivotal movement; said wire elements, the axis of said signal arm, and a pair of lines perpendicular to said axis and extending to the base extremities of respective of said wire elements, defining two adjacent acute substantially right triangles having common side portions along the axis of said signal arm and having adjacent acute angle apices; and resilient means for exerting a thrust axially of said arm for plac ing said wire elements under tension.

4. In a detector for combustible gas, a base member; a signal arm; a pair of wire elements having equal expansion characteristics responsive to a common temperature change therein, one of said elements constructed to include a catalyst for heating such element relative to the other element in response to the oxidation of combustible gas under the influence of such catalyst, each of said wire elements having a base and an outer extremity, the base extremities of said wire element being spaced apart and secured to said base member, th outer extremities of said wire elements being secured to said signal arm adjacent one extremity thereof; pivot means located between the axes of said wire elements for the opposite extremity of said signal arm; resilient means acting upon said signal arm in the region of said pivot means for urging such arm axially in a direction normally to maintain said wire elements under tension; the axis of said arm, said wire elements, and a pair of lines extending perpendicularly from such arm axis to respective of such wire base extremities normally defining two adjacent acute substantially right triangles having common side portions along the axis of said arm, said triangles having adjacent acute angle apices; and switch means operatively connected to said signal arm for actuation in response to angular movement of said arm.

5. In apparatus for the detection of combustible vapors, a pair of wires having equal expansion characteristics in response to a common temperatur change, and having unequal expansion characteristics in the presence of a combustible vapor; at base member, a base extremity of each of said Wires being secured to said base member; a signal arm; the opposite extremity of each of said wires being secured to said arm in the region of one end thereof; means in the region of said base member for pivotally mounting the other end of said arm; means for exerting a thrust axially of said arm for placing said wires under tension; said arm comprising a common side of two adjacent acute substantially right triangles having adjacent acute angle apices, th other sides of said triangles being geometrically defined by said wires and a pair of lines perpendicular to said arm and extending one each to said wire base extremities; and switch means operatively associated with said signal arm for actuation in response to angular motion of said arm.

6. In a detector for combustible gas, a base member; a signal arm; a pair of wire elements; said signal arm being positioned between said wire elements, one extremity of each of the latter being secured to said arm adjacent one extremity thereof, the opposite extremities of said wire elements being spaced apart and secured to said base member, two adjacent acutetriangles having common side portions along the axis of said arm and also having adjacent acute angle apices being geometrically defined by such wire elements, such axis of said. signal arm, and by a pair of lines extending perpendicularly from said axis to respective of said opposite Wire extremities; pivot means for the opposite extremity of said signal arm; resilient means for urging said signal arm resiliently and axially thereof in a direction normally to place said wire elements under tension, said wire elements having equal expansion characteristics responsive to a common temperature change, one of said wire elements constructed to include a catalyst for heating same relative to the other element in response to the oxidation of combustible gasunder the influence of such catalyst; and switch means operatively associated with said signal arm for actuation in response to angular movement of the latter.

7. In a detector for combustible gas, a pair of heat expansible wire resistance elements having equal expansion characteristics in response to a common temperature change, one of said elements constructed to include a catalyst for heating same relative to the other element in response to the oxidation of combustibl gas under the influence of such catalyst, each of said wire elements having an inner and an outer extremity;

a V-tension mounting for said wire elements comprising: a base member, a signal arm, means located in the region of said base member for pivotally supporting said arm, the inner extremity of each of said wire elements being spaced apart and secured to said base member, the outer extremity of each of said wire elements being secured to said arm thereby forming two adjacent triangle with said arm comprising a common side thereof and with acute angles at the adjacent apices thereof where said wire elements are secured to said signal arm, and resilient means for exerting an axial thrust upon said arm for placing said wire elements under tension; and signal means responsive to angular shifting of said signal arm.

CARTER TIFFANY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 350,388 Perry Oct. 5, 1886 692,007 Freym'an et al Jan. 28, 1902 1,467,911 Arendt Sept. 11, 1923 2,057,246 Morgan et a1. Oct. 13, 1936 2,299,815 Gent Oct. 27, 1942 2,306,509 T'almey Dec. 29, 1942 FOREIGN PATENTS Number Country Date 19,856 Great Britain Oct. 10, 1891 of 1890 736,243 France Nov. 21, 1932 

2. APPARATUS COMPRISING IN COMBINATION, A BASE MEMBER; A PAIR OF THEMO-RESPONSIVE EXPANSIBLE WIRE ELEMENTS MOUNTED WITH ONE EXTREMITY OF EACH THEREOF SECURED TO SAID BASE MEMBER AT SEPARATE LOCATIONS WHEREBY A STRAIGHT BASE LINE EXISTS BETWEEN SUCH LOCATIONS; A SIGNAL ARM HAVING THE OTHER EXTREMITIES OF SAID WIRE ELEMENTS SECURED ADJACENT ONE EXTREMITY OF SUCH ARM; MEANS FOR MOUNTING THE OPPOSITE EXTR EMITY OF SAID ARM FOR PIVOTAL AND AXIAL MOVEMENT IN THE REGION OF SAID BASE MEMBER SUBSTANTIALLY AT THE MID-POINT OF SUCH BASE LINE, MEANS FOR RESILIENTLY URGING SAID ARM AXIALLY FOR MAINTAINING SAID WIRE ELEMENTS UNDER TENSION SAID WIRE ELEMENTS, ARM AND BASESE LINE DEFINING TWO ADJACENT ACUTE SUBSTANTIALLY RIGHT TRIANGLES HAVING ADJACENT APICES AND HAVING A COMMON SIDE COMPRISING SAID SIGNAL ARM; ONE OF SAID WIRE ELEMENTS BEING CONSTRUCTED TO INCLUDE A CATALYTIC ELEMENT COMPRISING FINELY DIVIDED PLATINUM FOR HEATING SAME IN RESPONSE TO THE OCCURENCE OF A HYDROCARBON VAPOR IN THE PRESENCE OF OXYGEN WHEREBY AN EXPANSION DIFFERENTIAL MAY OCCUR BETWEEN SUCH ELEMENTS IN THE PRESENCE OF SUCH GASES, SAID ARM BEING ANGULARLY SHIFTABLE IN SIGNAL MEANS ACTUATABLE IN RESPONSE TO SUCH ANGULAR MOVEMENT OF SUCH SIGNAL ARM. 